Bi-level solenoid holding device

ABSTRACT

A solenoid device which is capable of suspending or supporting load devices at a first load level established mechanically and a second load level established electrically comprises a ferromagnetic base plate adapted to function as a solenoid core and a ferromagnetic holding plate hinged to the base plate. Spring means shaped to encircle the axis of the hinge strongly bias the holding plate against the base plate to provide a first and mechanical level for load retention. A solenoid coil received in the base plate closely interfits the base plate and, when energized electrically, provides a second level of power for load retention. The second level of power is rendered exceedingly efficient by a design in which the solenoid coil, except for lead connections, is fully immersed in a ferromagnetic medium which is free of air gaps.

United States Patent [1 1 Yost [ 1 July 15, 1975 [52] US. Cl. 335/253; 335/285; 335/296 [51] Int. Cl? A. IIOIF 7/08 [58] Field of Search 335/299, 298, 297, 296,

335/253, 254, 256, 258, 192, 275, 289, 285; 89/].5 R, 1.5 C, [.5 D; 294/83 AB [56] References Cited UNITED STATES PATENTS 2,59l 520 4/l952 Fligue 335/296 3,476,223 ll/l969 Hubbard 335/299 3,52l,209 7/1970 Fritz H 335/299 Primary ExaminerHarold Broome Attorney, Agent, or FirmDybvig & Dybvig ZZ\ Z0- II II n I] [57] ABSTRACT A solenoid device which is capable of suspending or supporting load devices at a first load level established mechanically and a second load level established electrically comprises a ferromagnetic base plate adapted to function as a solenoid core and a ferromagnetic holding plate hinged to the base plate. Spring means shaped to encircle the axis of the hinge strongly bias the holding plate against the base plate to provide a first and mechanical level for load retention. A solenoid coil received in the base plate closely interfits the base plate and, when energized electrically, provides a second level of power for load retention. The second level of power is rendered exceedingly efiicient by a design in which the solenoid coil, except for lead connections, is fully immersed in a ferromagnetic medium which is free of air gaps.

6 Claims, 4 Drawing Figures BI-LEVEL SOLENOID HOLDING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to solenoid holding devices and more particularly to holding devices operable at two levels, one of which is established mechanically and the other of which is established electrically.

2. Description of the Prior Art The following US. Pat. Nos. are representative of prior art relating to load holding devices:

l.522.792 2.8Jl.447 3.285.l32 2.430.6l 7 2.897.4l4 3.516.7ll2 2.485.003 1.200.707 3.578.373

SUMMARY OF THE INVENTION An exceptionally efficient magnetic flux medium for an electromagnetic device is produced by utilizing two ferro-magnetic bodies having closely matched planar surfaces which confront and abut one another. The only interruption to the matched and abutting ferromagnetic surfaces results from the presence of an annu lar recess formed in one of the abutting ferromagnetic bodies to receive and closely interfit a solenoid coil and the further presence of a lead wire passage. The result is an electromagnetic device which is substantially free of any intervening air gap and has a high holding power.

An additional mechanical holding power is provided by hinging the two ferromagnetic members remotely from the aftorementioned solenoid coil and providing spring means encircling the hinge axis which resists separation of the two ferromagnetic members. The spring means not only provides a second and mechanical holding power but also operates to mechanically resist the formation of an air gap between the two ferromagnetic members. A further feature of the present invention is that the resulting electromagnetic structure has an exceedingly low profile and is of pleasing appearance.

An object of the present invention is to provide a new and improved solenoid holding structure.

Another object of the present invention is to provide an electromagnetic device having a maximal flux path and a minimal air gap.

A further object of the present invention is to provide a solenoid holding device having two levels of holding power. one established mechanically and the other established electrically.

Other objects and advantages reside in the construction of parts. the combination thereof, the method of manufacture and the mode of operation. as will become more apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view ofa solenoid holding device in accordance with the present invention.

FIG. 2 is a section view taken substantially along the line 22 of FIG. 1.

FIG. 3 is a plan view with a portion broken away illustrating the base plate disassembled from the holding plate of the solenoid device.

FIG. 4 is an enlarged fragmentary section view taken substantially along the line 4-4 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The solenoid holding device comprises a base plate 10 which is of ferromagnetic material and which is shaped to have an upstanding circular boss 11 at one face thereof. Except as will be later described. the boss 11 has a planar surface and is contacted by an equally planar ferromagnetic holding plate 12. The holding plate. while otherwise generally circular, is formed with an outwardly extending foot 13 and diametrically oppositely therefrom an outwardly extending heel I6.

I'ntegrally formed on the heel 16 are lugs 14 which are spaced to straddle an interdigitating hinge member 28 integral with the base plate 10 and projecting outwardly therefrom as appears in FIG. 3. The hinge member 18 has a rounded upper surface 22 which permits the holding plate to swing upwardly without interfer ence from the member 18.

FIG. I of the drawing misleadingly suggests that the lugs 14 are not integral with the holding plate I2 but this is because the lugs 14 have been formed flat on their outer faces as they appear in FIG. 1. whereas the contour of the holding plate 12 is otherwise generally rounded.

The lugs 14 are hinged to the hinge member 18 by means of a hing pin 20 which is journaled in suitable apertures formed in the lugs 14 and in a bore 21 passing through the hinge member I8.

The holding plate 12 is biased strongly against the planar surfaces of the boss 11 by means of a spring member 24 which comprises a single strand of wire formed as shown in FIG. 1. More particularly. the wire is formed with loops 26 to loop twice about each end of the hinge pin 20. The axially outermost loop at each end of the pin 20 terminates as a strut 28, there being a strut 28 at each end of the spring member which projects adjacent and bears against the base plate 10. The two struts 28 approach closely one to the other below and slightly to the right of the hinge pin 20 as it appears in FIG. 2.

The spring member 24 is also formed with a triangular and centrally located bearer portion 30 which overlies the holding plate 12 as it appears in FIG. I.

The spring member 24 is so formed that when assembled about the hinge pin 20 as shown in FIGS. 1 and 2, the bearer 30 strives to swing downwardly toward the struts 28 but is blocked by the holding plate I2. Likewise. the struts 28 urged by a tension generated primarily in the loops 26 strive to approach the bearer 30 but are blocked by a side margin of the base plate 10. Accordingly. the spring member 24 exerts a substantial bias pressing the holding plate 12 into faee-to-face relation with the boss 11.

As best appears in FIG. 2, the base plate 10 has a shallow. cylindrically shaped cavity 32 formed therein underneath the foot 13. The foot 13 is bored in aligned relation to the cavity 32 to receive a shank 36 integrally joined to a conically formed latch member 34. As shown. the apex of the latch member 34, which is rounded. shallowly enters the cavity 32 and is. of course. retractable from the cavity 32 by any force effective to overcome the bias of the spring member 24 and thus lift the foot 13 upwardly from the base plate 10.

While the latch member 34 appears to abut the circular margin of the cavity 32 in FIG. 2, the latch member 34 is formed to a tolerance with respect to the height of the boss 11 that assures the latch member 34 is slightly undersized such that the holding plate 12 hottoms against the boss ll before the latch member 34 can abut the margin of the cavity 32.

The latch member 34 is an 80 cone in the sense that the side of the cone. except where rounded at the apex. extends at an angle of 40 to the plane of the base of the cone and thus the side of the cone subtends an angle of 80 about the axis of the shank 36. Accordingly. the shape of the latch member 34 is such that a taut or right string or wire of suitably small dimensions can be wedged to the right as appears in FIG. 2 and under the latch member 34, thereby causing the holding plate 12 to be lifted from the boss 11 and. when such string or wire has passed fully under the latch member 34 to the left as appears in FIG. 2. the latch member will return to shallowly enter the cavity 32 and thus entrap the string or the wire between the latch member and the boss II. A common application for such a latch mechanism requires the siezure ofa bomb arming ring of a size suitable that a portion of the ring can be wedged under the latch member 34. The spring 24 then provides a first holding level for the retention of load elements which have been wedged under the latch member 34 and entrapped in the space between the latch member 34 and the boss 11.

A second and substantially larger holding force is provided by electromagnetic components which will now be described. Formed within the body of the base plate 10 concentrically to the generally circular outer margin of the boss II is a generally toroidal channel or recess 40 having a rectangular cross section as seen in FIG. 2. The open side of the channel 40 directly confronts the holding plate 12. Remaining concentrically within the toroidal recess is a cylindrical core 41.

As apparent in FIG. 2, the coil 42 has been wound as a toroid having a substantially rectangular cross section. As appears in FIG. 4, however. the upper and lower faces of the coil are protected by insulating washers 44 which are preferably of a plastic composition. the interior edges of the washers being closely sized to the diameter of the core 4i. The washers 44 are affixed to opposite faces of the coil 42 by means of a heatshrinkable tape 46 which encircles the outer periphery of the coil 42 and. when heated. so shrinks that the side edges of the tape press smoothly against the washers 44. As a result of the tape 46 being heat-shrinked, the coil 42 is neatly retained in the desired toroidal shape.

The wire forming the coil 42 has an insulating varnish. not shown. or is otherwise insulated at its surfaces to prevent short circuits between the convolutions of the coil. The use of the insulating washers 44, together with the tape 42, is for sturdiness of the coil assembly and to allow packaging and handling of the coil assemblies without damage to the surface insulation of the wire forming the coil. It will be noted. however. that it is found unnecessary to provide an insulatng tape or the like to protect the inner periphery of the coil 42.

To allow electrical connection to the opposite ends of the coil 42, a relatively shallow access trough 50 has been cut across the upper face of the boss 11. as it ap pears in FIG. 3, such as to communicate between the outer circular wall of the boss and the channel 40. Re ceived in the trough 50 are coil lead wires 52 protected by suitable insulation 54. Those skilled in the art will understand that the lead wires 52 may be substantially greater in diameter than the wire forming the coil 42 and connected by solder or the like. not shown. to the opposite ends of the smaller wire of the coil 42.

As is apparent. the coil 42 has been so designed that a minimal amount of non-conducting material is used to protect the coil prior to its assembly into the channel 40. thus allowing a maximum number of turns of the wire forming the coil.

Inasmuch as the channel 40 is spaced inwardly from the outer margin of the boss I1 and inasmuch as the boss 11 makes firm face-to-face contact with the hold ing plate 12 except where interrupted by the trough 50 and the recess 40. the coil 42 is provided with a complete magnetic flux path productive of an exceptionally high magnetic efficiency. An examination of FIG. 2 will reveal that the coil 42 and its protective insulation together with its lead wires has. in effect, been fully immersed in a ferromagnetic medium with no air gap being present. Thus. both the core 41 and the margin of the boss 11 which surrounds the coil 42 make inti mate contact with the holding plate 12 except when interrupted by the trough 50.

A unique benefit residing in the holding device above desdribed is that the holding device presents a low and pleasing profile. Thus. it can be noted that the aggregate thickness of the plate members 10 and 12, when assembled in face contacting relation, said thickness measured parallel to the axis of the coil 42, is less than the inside diameter of the coil.

Although the preferred embodiment of this invention has been described. it will be understood that various changes may be made within the scope of the appended claims.

I claim:

1. An electromagnetic holding device comprising a pair of ferromagnetic plate members. each having a face portion. said plate members adapted for assembly in face confronting relation, one of said plate members having an annular channel in the face portion thereof. the face portion of the other of said members being uninterruptedly planar. means including a solenoid coil disposed in and substantially filling said channel, one of said plate members having trough means communicating to said channel from an exterior surface thereof. electrical lead means extending through said trough means having electrical connection to said coil, said ferromagnetic plate members cooperating to substantially fully immerse said coil and said lead means, and hinge means for hingedly joining said plate members adjacent one margin of each, said hinge means comprising interdigitating lug means integral with said plate members. and a hinge pin. said lug means having coaxially disposed bores receiving said hing pin.

2. The holding device of claim 1 including spring means for biasing said plate members into face contacting relation and adapted to yield to a pivotal movement of one of said members relative to the other about the axis of said hinge means.

3. The holding device of claim 2 including a latch member affixed to one of said plate members, the other of said plate members having a cavity to receive said latch member. said latch member and said cavity adapted to retain a load'when said plate members are in face contacting relation, said latch member separable from said cavity to release the load upon a pivotal separation of said plate members against the bias of said spring means.

4. The holding device of claim 3 in which said latch member is radially spaced from said hinge pin. said channel disposed between said latch member and said hinge pin.

5. The holding device of claim 3 wherein said spring means comprises a spring wire at least a portion of which is coiled about said hing pin.

6. The holding device of claim 5 wherein said spring 

1. An electromagnetic holding device comprising a pair of ferromagnetic plate members, each having a face portion, said plate members adapted for assembly in face confronting relation, one of said plate members having an annular channel in the face portion thereof, the face portion of the other of said members being uninterruptedly planar, means including a solenoid coil disposed in and substantially filling said channel, one of said plate members having trough means communicating to said channel from an exterior surface thereof, electrical lead means extending through said trough means having electrical connection to said coil, said ferromagnetic plate members cooperating to substantially fully immerse said coil and said lead means, and hinge means for hingedly joining said plate members adjacent one margin of each, said hinge means comprising interdigitating lug means integral with said plate members, and a hinge pin, said lug means having coaxially disposed bores receiving said hing pin.
 2. The holding device of claim 1 including spring means for biasing said plate members into face contacting relation and adapted to yield to a pivotal movement of one of said members relative to the other about the axis of said hinge means.
 3. The holding device of claim 2 including a latch member affixed to one of said plate members, the other of said plate members having a cavity to receive said latch member, said latch member and said cavity adapted to retain a load when said plate members are in face contacting relation, said latch member separable from said cavity to release the load upon a pivotal separation of said plate members against the bias of said spring means.
 4. The holding device of claim 3 in which said latch member is radially spaced from said hinge ppin, said channel disposed between said latch member and said hinge pin.
 5. The holding device of claim 3 wherein said spring means comprises a spring wire at least a portion of which is coiled about said hing pin.
 6. The holding device of claim 5 wherein said spring wire has a second portion spaced along the length of said hinge pin from the first mentioned portion and also coiled about said hinge pin, said spring wire terminating at each end thereof with a strut bearing against one of said plate members, said spring wire having an intermediate portion innerconnecting said coiled portions and bearing against the other of said plate members. 